1. Field of the Invention
The present invention relates to a navigation device.
2. Description of the Related Art
Conventionally, a vehicle navigation device, based on a detected current position of the vehicle and a destination set by the driver, and the like, searches for a route from the current position to the destination so that the vehicle can travel in accordance with the searched route. In addition, automatic transmission control systems have been developed to provide control based on navigation information and current position information received from the navigation device.
FIG. 2 is a block diagram of a conventional navigation device which includes a CPU 11 for overall control of the entire navigation device, a work memory (RAM) 12 used by the CPU 11 to temporarily store various data, such as route and guidance information, a ROM 13 in which various programs for searching a route to a destination and for providing guidance along the route, as well as a control program are stored, and a current position detection processing section 15. A GPS 16 and a gyro 17 are connected to the current position detection processing section 15. The GPS 16 receives radio wave transmissions from a satellite to detect the current position. The gyro 17 detects the yaw of the vehicle and integrates the detected yaw to determine the direction of the vehicle.
Further, the navigation device is provided with a driver 18 and a read/write device 19 for reading a data storage medium in which road condition data is recorded and for writing data onto the storage medium.
The navigation device also has a communication interface (I/F) 20 serving as a communication section, a communication device 21 connected to the communication interface 20, a semicustom IC 24, such as an application specific integrated circuit (ASIC) for example, for a specified drawing function, and a display device 25 connected to the ASIC 24. The navigation device is further provided with a voice LSI 26 to which a voice input/output device 27 is connected.
The display device 25 includes a screen for display of operation guidance, operation menus, operation keys, a guidance route 1 displayed with the current position, and map of areas around the current position. The display device 25 may be a CRT display, a liquid crystal display, a plasma display, or a hologram device which projects a hologram on a front glass.
The voice input/output device 27 includes a microphone, a voice synthesizer, and a speaker (not shown) for input of information by means of voice and output of guide information through the speaker as a voice synthesized by the voice synthesizer.
The navigation device also has a vehicle interface (I/F) 28 which allows the navigation device to operate in conformance with the vehicle in which the navigation device is installed. The navigation device receives, via the vehicle interface 28, vehicle information from the engine controller which controls the engine, the automatic transmission controller which controls the automatic transmission, and various sensors (an engine speed sensor, a throttle opening sensor, and a vehicle speed sensor, and the like).
A power source (not shown) generates a predetermined voltage for operating the various components including the CPU 11, the work memory 12, the ROM 13, the current position detection processing part 15, the GPS 16, the gyro 17, the driver 18, the player 19, the communication interface 20, the communication device 21, the ASIC 24, the display device 25, the voice LSI 26, the voice input/output device 27, and the vehicle interface 28. An input device (not shown) can be connected to the CPU 11 for correcting the current position when the vehicle starts running and for inputting a destination.
In the navigation device described above, the CPU 11 executes the guidance and display routines, whereby a current position and a map of the area around the current position are displayed on the display screen of the display device 25. When a driver of the vehicle operates the input device to set a destination, the CPU 11 executes a route search to provide a recommended route from the current position to the destination, and when such a route is determined, executes guidance with display of current position and a map of the area around the current position on the display screen whereby the vehicle""s driver can follow the recommended route.
However, in the conventional navigation device, if the specifications of the various components such as the GPS 16, the gyro 17, the read/write device 19, the communication device 21, the display device 25, the voice input/output device 27, the engine control device, the automatic transmission control device, and the sensors are different, the internal communications (LAN) between the GPS 16, the gyro 17 and the current position detection processing section 15, between the read/write device 19 and the driver 18, between the display device 25 and the ASIC 24, between the voice input/output device 27 and the voice LSI 26, and between the engine control device, the automatic transmission control device, and the sensors and the vehicle interface 28 may differ, as will external communication between the communication interface 20, the communication device 21 and an external (remote) communication center (not shown). As a result, the specifications for the detection signals, control signals, various data, and power voltages become different. Further, if the specifications of other accessories such as audio equipment, video, and radio to be mounted on the navigation device are different, the specifications of the control signal to be transmitted between other components (not shown) may be different, or the specifications for the power voltages may be different.
Therefore, it is necessary that each navigation device be individually designed and manufactured for each model vehicle, which is provided with components having different specifications, or for each model vehicle which is equipped with other components with different specifications. These problems of compatibility/incompatibility between the various components lead to corresponding problems of mounting the navigation device in a given vehicle and cost.
Accordingly, one object of the invention is to provide a navigation device with improved mountability and reduced cost by solving the above-mentioned problems.
Therefore, the navigation device of the invention includes a main processing unit provided with a CPU and a memory, a sub-processing unit connected to the main processing unit, connection means for connecting the main processing unit and the sub-processing unit, and component(s) connected to the sub-processing unit.
In another embodiment of the present invention, the main processing unit is further provided with a drawing section having a drawing function. The components connected to the sub-processing unit include current position detection means for detecting a current position and a data recorder for recording data.
In still another embodiment of a navigation device of the invention, the main processing unit is further provided with a component identification means for identifying the components(s) connected to the sub-processing unit. The component identification means may identify the component by judging the type of the sub-processing unit.
In yet another embodiment of the navigation device of the invention, the sub-processing unit is further provided with a component identification information generation means for generating component identification information. The component identification means identifies the component based on the component identification information.
The aforementioned connection means may be a general-purpose interface.
In still another embodiment of the invention, the main processing unit is formed of three or more stacked circuit boards, and the sub-processing unit is formed of two or less circuit boards.
As described above, according to the present invention, the navigation device includes a main processing unit provided with a CPU and storage means, a sub-processing unit connected to the main processing unit, connection means for connecting the main processing unit and the sub-processing unit, and the component connected to the sub-processing unit. In this case, even if the specifications of the components connected to the sub-processing unit are different, the components of the sub-processing unit can be designed and manufactured for compatibility with the various components, whereby the main processing unit can be designed and manufactured as a general-purpose product. Therefore, not only the mountability of the navigation device can be improved, but also the cost thereof can be reduced.
In another embodiment of the invention, the main processing unit is provided with a component identification processing means for identifying the component(s) connected to the sub-processing unit, for determining the specifications of the component(s), and for, based on the results of that determination, generating control signals and data for transmission to the sub-processing unit.
In still embodiment, the component identification processing means identifies the component by further judging the type of the sub-processing unit. By judging the type of the sub-processing unit, the component identification processing means can identify the component connected to the sub-processing unit and can determine the specifications of the component. Accordingly, based on the result of determination, control signals for the sub-processing unit and various data are generated and transmitted to the sub-processing unit.
In still another embodiment of the invention, the sub-processing unit is further provided with a component identification information generation means for generating identification information. The component identification processing means identifies the component based on the component identification information and determines the specifications of the component.
In another preferred embodiment of the invention, the main processing unit is formed of three or more stacked circuit boards, and the sub-processing unit is formed of two or less circuit boards. By stacking the circuit boards of the main processing unit, the generation of noise in the bus can be suppressed. In addition, since the sub-processing unit is formed of two or less circuit boards, the cost of the navigation device can be reduced.